Field of the Invention
The present invention relates to a hybrid vehicle and a braking method thereof, and more particularly, to a hybrid vehicle which adaptively varies a braking method based on braking situations, and a braking method thereof.
Discussion of the Related Art
In general, a hybrid vehicle using two or more different types of power sources refers to a vehicle which is driven by an engine that acquires driving force by burning a fuel and a motor that acquires driving force from power of a battery. In such a hybrid vehicle, when braking control by a brake pedal is executed during driving of the vehicle, a motor assisting output torque of an engine enters regenerative braking and captures deceleration energy thus charging a battery. In other words, regenerative braking is technology in which electric energy is generated by applying counter-torque to a motor using energy generated during braking and the generated electric energy is stored in a battery.
In such regenerative braking, when a driver's braking demand is detected, a hybrid control unit (HCU) is configured to calculate a total amount of braking and calculate an amount of regenerative braking based on an operating state of the motor and a current gear. Further, an electronic brake system (EBS) satisfies braking, acquired by subtracting the amount of regenerative braking from the total amount of braking, through an amount of hydraulic (friction) braking. In other words, braking of the hybrid vehicle is performed by cooperative control between the hybrid control unit (HCU) that executes hydraulic braking and the electronic brake system (EBS) that executes regenerative braking.
However, in a transmission mounted electric device (TMED) type hybrid vehicle to which a multi-range transmission is connected, an amount of regenerative braking is estimated based on real torque of a motor disposed at the front end of the transmission. However, when the amount of regenerative braking is estimated based on real torque of the motor, there is a difference between braking force demanded by a user and braking force based on real torque of the motor due to a time delay occurring between a point of time when the user demands braking and a point of time when braking is executed based on real torque of the motor. Such a difference may cause unnecessary power loss.